Silver coat lets Saharan ants withstand scorching desert heat

IT’S fashion front line, not fashion faux pas. During the hottest part of the day, when sand temperatures reach 70 °C, the hairy back of the Saharan silver ant repels the sun’s rays and sheds excess heat.

Nanfang Yu from Columbia University in New York was intrigued by how each ant looked like “a droplet of mercury”, so took a closer look.

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Yu’s team found that the ants’ silvery appearance comes from a dense array of Toblerone-shaped hairs, which reflect visible and near-infrared light. The hairs are about the same thickness as the wavelength of the sun’s warming rays, so the rays bounce off their triangular walls.

The hairs are much thinner than the wavelengths of mid-infrared light so they allow those wavelengths of light to radiate away from the ants – effectively cooling them down. Ants with hair had body temperatures between 5 and 10 °C lower than those that had been shaved (Science, doi.org/5jc).

Their silvery coats allow the ants to scavenge the corpses of less-fortunate insects and arthropods under the midday sun.

This article appeared in print under the headline “Hairy back keeps Saharan ants cool”